JPS58117745A - Encryption device - Google Patents

Abstract

PURPOSE:To keep the confidentiality of the pattern synchronism control procedure of an encryption device, by constituting a synchronism control pattern which had been fixed conventionally into a variable synchronism control pattern which is selected by a key. CONSTITUTION:When the synchronism of encryption is taken, the synchronism control patterns F(PNi(+)),F(PNj(+)) are multiplexed to a synchronism control channel while being changed sequentially at a transmission side. Since the synchronism control patterns F(Ki(d)),F(Kj(d)) are not detected from the synchronism control channel, the encryption synchronism control is not done at a reception side. When the encryption synchronism is unlocked, the synchronism control patterns F(Ki(d)),F(Kj(d)) designated with the keys Ki(d),Kg(d) are multiplexed to the synchronism control channel and a synchronism initial data RS is multiplexed to a data channel in place of the encrypted data at the transmission side. Since the synchronism control patterns F(Ki(d)),F(Kj(d)) are detected from the synchronism control channel at the reception side, the encryption synchronism control is done between the transmission and reception sides to establish the synchronism of encryption.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cryptographic method for establishing cryptographic synchronization using a synchronization control pattern, and more particularly to a concealment method for a pattern synchronization control procedure.

Conventionally, this type of cryptographic apparatus has adopted a method that combines a 7-rem synchronization method and a control pattern cipher synchronization method.

A flowchart of the pattern synchronization control procedure in this method is shown in FIG. In this method, a tunnel control channel dedicated to the cryptographic device is included in the encrypted data string to be sent, and this synchronization control channel is used to establish cryptographic synchronization. Normally, when cryptographic synchronization is established, on the sending side (shown in Figure 1 (1)), →1-1→1-2→1
-3→1-4→1-5nl-1→(<J) return), and on the receiving side (shown in Figure 1(b)), →2-1→2-2→ 2-3→2-4→2-1→
The pattern synchronization control procedure is as follows.If encryption synchronization is established, the transmitting side multiplexes the synchronization control pattern 81=i on the synchronization control channel.The receiving side Since the synchronization control pattern S1 is detected from the synchronization control channel, cryptographic synchronization control is not performed.

When encryption synchronization is lost, on the sending side, →1-6→1-7
→ 1-8 → 1-4 → 1-5 → 1-6 → (<return>) pattern synchronization control procedure, on the receiving side → 2-1 → 2
The pattern synchronization control procedure is -2 → 2-5 → 2-6 → 2-3 → 2-4 → 2-1 → (repeat). channel 8
The synchronization control pattern of 2 is multiplexed, and the initial value data for cipher synchronization R8\tdata is used instead of the encrypted data. Multiplex to channel. On the receiving side, 82 from the synchronization control channel
Because the synchronization control pattern is detected.

Initial value data for cryptographic synchronization Rst- from the data channel
Then, cryptographic synchronization control is performed between the sender and the receiver, and cryptographic synchronization is established.

Therefore, when the cryptographic device having the pattern synchronization controller IN described above is used, for example, in wireless communication.

Eavesdropping in the wireless section is easy. Further, as the synchronization control pattern, a pattern with strong autocorrelation is usually used, and the control patterns 81 and 82 are fixed patterns, and the control patterns can be known from the hardware of the L cryptographic device. For the above two reasons, it is possible to detect LIK control patterns S1 and 82 by interception. The pattern synchronization control procedure of the cryptographic device becomes known. Moreover, since the control pattern 82 was detected and the cryptographic synchronization initial value data R8 was also known at the same time, there was a risk that it would be possible to predict the key being cryptographically processed. .

The present invention eliminates omissions in the pattern synchronization control procedure of the cryptographic device due to eavesdropping, etc. by changing the conventional fixed synchronization control pattern to a variable synchronization control pattern that can be selected using a key. The present invention provides an encryption method that makes it possible to prevent the ability to predict a key from being compromised.

Next, an embodiment of the present invention will be described with reference to FIG.

The present invention aims to solve the drawbacks of the conventional method.

The conventionally fixed synchronous control pattern (8 shown in Figure I!1)
1.82), a method was used in which a specific code at was selected from a set of code words having an appropriate table distance. Here, F(X) is the code i[
tlkI, and the set S of code words is a collection of codes having an appropriate distance between codes. This number of code words t−
N(!nee j and its codeword set S are 5=(x
l F(X), 04X4N-1),! :H can be done.

is selected from nine sets S of synchronous control patterns (8
2) When selecting t-, the number to be selected is expressed as a key and is written as K(d) (mod N), then 1 is selected and 9 synchronous control patterns (82 shown in Figure 1) are F(K
It can be expressed as (d)). In addition, the synchronization control pattern (81 shown in Figure 1) uses rounding, pseudorandom numbers PN (-1-), (mod N), which must be different each time it is sent.
f: is used to select from the set S, and the nine selected synchronous control patterns (81 shown in Figure 1) are F(PN(t)).
It can be expressed as However, make sure that K(d) = P N←) does not occur.

Normally, when cryptographic synchronization is established, the sending side (see Figure 2 (J
l)), →3-1→3-2→3-3→3-4
→(3-9→3-10→3-4)→3-5→3-6→3
-7 → 3-8 → 3-1 → (combination return) pattern synchronization control procedure, reception 11 (shown in Figure 2 (b)) →
4-1→4-2→4-3→4-4→4-5→4-1→(
A pattern synchronization control procedure is used.

In other words, if cryptographic synchronization is established, on the sending side,
Synchronous control pattern F (PNi(
+)), F(PNj(-t-)) are multiplexed while being changed sequentially. On the receiving side, from the synchronization control channel,
Synchronous control pattern F (K t (a)).

If F(Kj(d)) is not detected, rounding and cryptographic synchronization control is not performed. When the cryptographic synchronization is lost, on the sending side, →
3-1→3-2→3-14→3-15→3-16→3-
The pattern synchronization control procedure is 7 → 3-8 → 3-1 → (combination), and on the receiving side → 4-1 → 4-2 → 4-3 → 4
-6 → 4-7 → 4-4 → 4-5 → 4-1 → (<9 returns)
Take the pattern synchronization controller at.

When the cryptographic synchronization is lost, the transmitting side uses the synchronization control pattern F (K i (d) ), F specified by the key K i (d) t K j (a) on the synchronization control channel.
(K j (d)) is multiplexed, and initial value data R8 for cryptographic synchronization is multiplexed onto the data channel instead of the encrypted data.

On the receiving side, since the synchronization control patterns F (K1(d)) and F (Kj(d)) are detected from the synchronization control channel, the initial cryptographic synchronization data R8 is extracted from the data channel, and the All encryption synchronization control is implemented with
Establish crypto synchronization. Moreover, the synchronous control pattern F (K
i (d) ) , F (K j (d) ) t-
When changing, on the sending side → 3-1 → 3-11 → 3
The pattern synchronization control procedure is -12→3-13→, and the receiving side takes the pattern synchronization control procedure →4-1→4-8→4-9→4-10→. In the above example, the synchronization control pattern is a combination of two codes F(PNi(,1-)
), F(PNj(-1-)) and F(K1(d)
).

F (K j (d)) t- was used. This means that when the set 8 of codewords to be used is removed from the hardware,
When F(K i (d) ) is used in Hayabusa, F(K i (d) ) becomes F(Ki
It is observed that (d)) is not multiplexed on the synchronization control channel, and it turns out that F(Ki(d)) is a synchronization control pattern that implements cryptographic synchronization control.
(K i (d)), F (K j (d))
If the combination of F (K 1 (d)),
F (PN j (+)) or P (PNi (g)), F
Since the combination of (Kj(d)) is multiplexed, even by long-term interception, F(Ki(d)),
It becomes difficult to predict the synchronization control pattern of F (K j (d)).

As explained above, the present invention changes the conventionally fixed synchronization control pattern to a variable synchronization control pattern that can be selected using a key. It is possible to prevent giving clues to predict the key being processed.

To give an example of this effect, for example, if the number of code words in the set S is Ni1O', then according to the embodiment, the code word 2
[If 1 is combined to form a synchronization control pattern, the number of combinations of the patterns is N. becomes 1013. Therefore, when predicting a synchronization control pattern to implement cryptographic synchronization control from among them, the accuracy rate P is 10-1! It is. This value varies depending on the conditions required of the encryption device, but once a day.

If you want to update the key for selecting the synchronization control pattern, 1
Approximately 107 synchronous control patterns must be fully verified per second. (Verification is to determine whether the pattern to be checked is a synchronization control pattern that implements cryptographic synchronization control.) At the current technological level, it is impossible to prepare a verification device with such a function. In addition, during the inspection, it is necessary to perform interference to cause cryptographic synchronization to occur, and to perform cryptographic synchronization. Since synchronization is abnormally high, some sort of warning will be given to the cryptographic device operator.

[Brief explanation of the drawing]

FIGS. 1(1) and 1(b) are flowcharts showing the pattern synchronization control procedure of a conventional cryptographic device, and FIGS.
(b) is a flowchart showing an embodiment of a pattern synchronization control procedure in the present invention. Father-in-law / Figure<b, + 1 par 2 Fusako (b)

Claims (1)

[Claims] In an encryption method that establishes cryptographic synchronization using a synchronization control pattern, it is better to prepare a number of predetermined synchronization control patterns and select and use a synchronization control pattern that performs cryptographic synchronization using a key from among them. , a cryptographic method characterized by concealing a pattern synchronization control procedure.